This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The accessory gene vif of lentiviruses is required for efficient viral replication. Vif inhibits virion incorporation of a cellular cytidine deaminase, APOBEC3G, by targeting this cellular protein for proteosomal degradation. A vif-deleted virus may be persistent in the host, although at extremely low levels and restricted to specific tissues or cell subsets with reduced expression of APOBEC3 proteins.